Check valve



FIG. 1 is a perspective view taken from the front and right side of a check valve, showing our new design;

FIG. 2 is a top plan view thereof;

FIG. 3 is a rear elevational view thereof;

FIG. 4 is a left side elevational view thereof;

FIG. 5 is a bottom plan view thereof; and

FIG. 6 is a sectional view taken along line 6--6 of FIG. 4. 

The ornamental design for a check valve, substantially as shown. 